1. Field of the Invention
The present invention relates to optical communication equipment and, more specifically, to equipment for WDM communication systems.
2. Description of the Related Art
To achieve high transmission capacity, wavelength-division multiplexing (WDM) communication systems should have relatively high spectral efficiency. For example, to achieve a capacity of 1.2 Tbit/s, a WDM system operating over a wavelength range of about 25 nm (3.1 THz) should have a spectral efficiency of about 0.4 bit/s/Hz. This corresponds to a channel spacing of about 0.8 nm (100 GHz) for a bit rate of 40 Gbit/s. With WDM channel packing this dense, narrow bandpass filtering should be employed to provide good channel isolation/crosstalk reduction. However, this filtering also results in optical waveform distortion, which increases the number of decoding errors at the receiver. It is therefore desirable to have a method of signal transmission that would mitigate the effects of narrow bandpass filtering in dense WDM communication systems.